One serious problem with rotary dial padlocks is that they cannot be used in the dark or by handicapped people. Indeed, even dexterous, fully-sighted persons have difficulty with rotary dial locks. Further, rotary dial operation is slow and the settings are not positive, that is, they are imprecise and do not stay put.
Push-button locks offer the relative pick-resistance of rotary dial locks in that they are combination locks, and also can be opened in the dark or by sightless or physically handicapped persons. They also have positive action.
However, prior push-button locks of the 10-button type do not offer a sufficient number of combinations for institutional use. Further, prior push-button locks are as difficult to open as the rotary dial locks when the combination is lost or forgotten. Normally these locks are destroyed or rendered useless in the process of opening.
In addition, in institutional settings such as schools, there is dual authorization requirement. The school in effect rents locker space to students and provides a school-owned lock. The school retains authority to open the lock at all times. That authority supercedes the student's right and usage of the locker. For example, the school may need to open the lock for the student who forgets or looses his/her combination, who fails to clean out his/her locker at the end of the term or when leaving school during the term, or the school may have a need to inspect the locker for unauthorized articles or contraband.
It is very inconvenient for a school to have to keep handy all the locker lock combinations, because ease of access to combination lists means there is no security for combination information. Further, it is very tedious when at a given time all the lockers must be opened, e.g. at semester end. Consulting combination lists, matching serial numbers to individual locks, and opening hundreds or thousands of locks in a short time is burdensome to the point of near impossibility.
Accordingly, there is a clear need in the art for a lock that has positive action, has the security of a combination, is easier to use than a rotary type, is cheap, can be used in the dark or by sightless or handicapped persons, and has a bypass opening system for persons having overriding authority.
This invention solves those problems by providing a 15-button push-button lock having a secondary keyed unlocking system, which secondary lock can have a common cylinder keyed all the same for institutional use so that one unique master key can open all the locks in the school, regardless of serial number or combination. The addition of the secondary key prolongs the service life of the locks.